JP2011247462A - Loop type heat pipe and evaporator manufacturing method of the loop type heat pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the structure of a loop type heat pipe and a method for manufacturing the same.SOLUTION: In the loop type heat pipe wherein a working fluid is circulated to an evaporator and a condenser via a pipe, the evaporator is provided with a casing having a groove formed in the inner wall thereof and a wick having a metal pattern matched with the shape of a groove top of a groove formed on the outer wall surface thereof and evaporating the working fluid flowing in from a tube. The wick is housed in the casing so that the groove top and the metal pattern are opposed to each other and the groove top and the metal pattern are subjected to diffusion bonding.

Description

  The present invention relates to a structure of a loop heat pipe and a method for manufacturing an evaporator of the loop heat pipe.

  A heat pipe is a device that uses latent heat of liquid evaporation and condensation, and is widely used for heat dissipation of electronic devices such as computers. One type of heat pipe is a loop heat pipe. FIG. 8A shows a principle diagram of the loop heat pipe, which shows that the evaporator 10, the condenser 20, and the vapor pipe 30 and the liquid pipe 40 that connect them are configured. Inside these, ammonia or chlorofluorocarbon is sealed as a working fluid at a constant pressure. The heating element is arranged in close contact with the evaporator 10, and heat from the heating element is conducted to the evaporator 10, and the working fluid changes from the liquid phase to the gas phase by this heat in the evaporator 10. The working fluid changed to the gas phase moves to the condenser 20 through the vapor pipe 30 with the heat absorbed by the evaporator 10. Here, the heat absorbed by the working fluid is dissipated, changes from the gas phase to the liquid phase again, returns to the evaporator 10 through the liquid pipe 40.

  FIG. 8B shows the internal structure of the evaporator 10, and FIG. 8C shows the A-A 'cross section of FIG. 8B. A plurality of groove-shaped grooves (steam discharge grooves) 11 extending in the axial direction are formed on the inner wall of the housing of the evaporator 10. The cylindrical wick (porous body) is in contact with the groove 12 of the groove 11. ) 13 is inserted. The wick 13 has a hollow portion 14, and the liquid-phase working fluid sent from the liquid tube 40 to the wick 13 accumulates in the hollow portion 14, penetrates the fine holes of the wick 13 by capillary action, and the outside of the wick 13. It oozes on the surface. At this time, the heat from the heating element that is in close contact with the evaporator 10 is conducted to the surface of the wick 13 through the groove on the inner wall of the housing of the evaporator 10, and the working fluid evaporates by the heat and the gas phase It becomes a working fluid and absorbs heat to cool the heating element. The gas-phase working fluid that has absorbed heat passes through the groove 11, reaches the vapor pipe 30, and moves to the condenser 20. Thus, the working fluid circulates and the phase change is repeated, whereby the heating element is continuously cooled.

  As described above, since the heat from the heating element is conducted to the wick 13 through the casing of the evaporator 10 to evaporate the working fluid, the loop heat pipe evaporates the working fluid 12 and the wick 13. It is important that the two come into close contact with each other and efficiently conduct heat. If this contact is incomplete, heat is not sufficiently transferred to the wick 13 and the efficiency of evaporation is reduced, resulting in a decrease in the cooling performance of the loop heat pipe.

  In order to increase the efficiency of heat conduction from the evaporator 10 to the wick 13, a porous metal layer may be provided between the groove formed on the inner wall of the evaporator housing and the contact surface of the wick that is in close contact therewith. Are known.

U.S. Pat. No. 4,765,396 Japanese Patent No. 3450148

  As described above, the quality of close contact between the inner wall of the housing of the evaporator of the loop heat pipe and the wick affects the cooling performance. However, the wick deforms due to thermal strain applied to the wick during loop heat-hype operation or mechanical stress applied to the wick during assembly of the evaporator, creating a gap and incomplete contact between the groove and the wick surface. In some cases, there is a problem that the cooling performance is lowered.

  It is also known to provide a porous metal layer on the outer surface of the wick to improve the thermal conductivity between the groove and the wick formed on the inner wall of the evaporator. However, because the porous metal layer and the groove are in close contact with each other by mechanical pressure, a gap is formed by thermal stress or mechanical stress as described above, and the thermal resistance at the contact surface is large. There is a risk that the thermal conductivity decreases.

  An object of the present invention is to provide a loop heat pipe having high cooling performance without generating a gap even when thermal stress or mechanical stress is applied.

  According to one aspect of the invention, a loop heat pipe that circulates a working fluid to an evaporator and a condenser via a pipe, the evaporator includes a casing formed with a groove on an inner wall, and a groove of the casing. A metal pattern that matches the shape of the groove is formed on the outer wall surface, and a wick that evaporates the working fluid flowing in from the pipe is provided, and the housing is configured to accommodate the groove and the metal pattern relative to each other. There is provided a diffusion-bonded loop heat pipe that diffuses a metal pattern into a metal forming the metal.

  According to another aspect of the invention, a loop-type heat pipe that circulates a working fluid to an evaporator and a condenser via a pipe, the evaporator forms a groove in the housing and the outer wall, and the groove groove And a wick that evaporates the working fluid flowing in from the tube, and a diffusion-bonded loop heat pipe that diffuses the metal film of the ridge of the wick into the metal that forms the inner wall of the housing is provided. .

  According to another aspect of the invention, a metal film forming step of forming a metal film with a predetermined width and interval on the upper and lower outer wall surfaces of a flat rectangular parallelepiped wick, on the metal pattern The insert metal was placed in the insert metal placement step of placing the insert metal, and in the housing of the metal evaporator in which the first groove crest was formed in the shape of the metal pattern on the bottom surface of the inner wall of the flat box type. The wick is placed in alignment with the metal pattern on the lower surface of the wick and the first groove crest, and a metal lid having a groove formed on one surface in accordance with the shape of the metal groove is formed on the wick. A wick accommodation step of placing a lid with the metal pattern on the upper surface aligned with the second groove crest, a welding step of fusing the joint surface between the housing housing the wick and the lid, and the deposited evaporator at a predetermined temperature With heat and insert Evaporator manufacturing method of the loop heat pipe comprising genus wick metal pattern and the diffusion and bonding step of diffusing the metal of the first and second Mizoyama, is provided.

  Further, according to another aspect of the invention, a wick groove forming step of forming strip-shaped grooves at predetermined widths and intervals on the upper and lower outer wall surfaces of a flat rectangular parallelepiped wick, and a metal film on a groove mountain of the wick groove The groove metal film forming step for forming the insert metal, the insert metal placing step for placing the insert metal on the metal film, and the wick with the insert metal placed in the housing of the metal evaporator, are arranged on the upper surface of the wick. A wick housing process for placing a metal lid, a welding process for welding the joint surface between the housing housing the wick and the lid, and heating the welded evaporator at a predetermined temperature to insert metal into the wick metal There is provided a method for manufacturing an evaporator of a loop heat pipe, comprising: a diffusion bonding step of diffusing into a metal of the film and first and second groove crests.

  The groove on the inner wall of the evaporator housing and the metal pattern on the outer wall surface of the wick are integrated by diffusion bonding, so that high cooling performance can be achieved without generating gaps even if thermal or mechanical stress is applied. A loop-type heat pipe can be provided.

It is a structural example of the evaporator of the loop type heat pipe of the present invention. It is a manufacturing flow (the 1) of the evaporator of Example 1. FIG. It is a manufacturing flow (the 2) of the evaporator of Example 1. FIG. 2 is an enlarged view of a wick outer surface portion of Example 1. FIG. 3 shows a method for forming a metal pattern of Example 2. It is a manufacturing flow (the 1) of the evaporator of Example 3. FIG. It is a manufacturing flow (the 2) of the evaporator of Example 3. FIG. It is an example of a loop type heat pipe.

Example 1
A structural example of the evaporator 100 of the loop heat pipe of the present invention will be described with reference to FIG. The loop heat pipe of the present invention has the same configuration except for the evaporator 10 of the loop heat pipe shown in FIG.

  FIG. 1A shows an example of the appearance of the evaporator 100, and a vapor pipe 30 and a liquid pipe 40 are connected to the evaporator 100. In order to describe the internal structure of the evaporator 100, FIG. 1 (b) shows the AA ′ cross section shown in FIG. 1 (a), and FIG. 1 (c) shows the BB ′ cross section shown in FIG. 1 (b). Indicates.

  As shown in FIGS. 1B and 1C, the exterior of the evaporator 100 includes a box-type casing 101 and a lid 102 covering the casing 101, and each material is, for example, Cu (copper). Then, grooves (grooves) 110 each having a width and a height of 1 mm in the longitudinal direction inside the casing 101 and the inner side of the lid 102 (the direction in which the steam pipe 30 and the liquid pipe 40 are connected in FIG. 1) are spaced at 1 mm intervals. It is formed in a stripe shape.

  Inside the housing 101, for example, a ceramic wick 130, which is a porous body (average pore diameter 2 μm, porosity 60%) obtained by sintering alumina powder, is accommodated. The shape of the wick 130 is a flat rectangular parallelepiped shape that matches the housing 101, and has a hollow portion 140 that stores a working fluid therein. One of the hollow portions 140 is open, and the opening and the liquid pipe 40 are connected to each other so that the working fluid flows in and the other is closed. The working fluid in the hollow portion 140 oozes out to the outer surface (herein referred to as “outer surface” in order to be distinguished from the surface in the hollow portion 140) through the porous body by capillary action. The surface of the wick 130 is heated by the heat conducted from the casing 101 and the lid 102, and the working fluid that has oozed out to the surface of the wick 130 becomes steam, but the working fluid that has become steam (gas-phase working fluid) is the groove 110. Through the steam pipe 30. The opening of the wick 130 is sealed with a seal member 160 so that the working fluid does not flow through the porous body and does not flow directly into the housing 101.

  On the outer surface of the wick 130, a metal pattern 150 made of Cu, for example, is formed in accordance with the groove 120 of the groove 110 formed in the housing 101 and the lid 102. The metal pattern 150 and the metal forming the groove 120 of the casing 101 and the lid 102 are diffusion-bonded and integrated (details will be described later). That is, the heat from the heating element that is in contact with the exterior of the loop heat pipe 100 (comprising the casing 101 and the lid 102) is transferred to the wick 130 via the exterior through the diffusion junction. The structure according to the prior art has a joint surface between the exterior inner wall and the wick, and the thermal resistance is small when the joint surface is in close contact, but the thermal resistance is large when a gap occurs in the joint surface due to thermal or mechanical stress. However, the thermal conductivity is lowered, but the integration of the present invention can suppress the lowering of the thermal conductivity.

  Next, a manufacturing flow of the evaporator 100 of the loop heat pipe of the present invention will be described with reference to FIGS. In the description process, FIG. 4 in which the outer surface portion of the wick 130 is enlarged is used as an auxiliary. 2 and 3 are cross-sectional views taken along the line B-B 'shown in FIG.

  First, a surface treatment is performed on the wick 130 in order to improve the adhesion between the metal film and the wick surface in the next step. Examples of the surface treatment method include a method using a coupling agent and a method of irradiating with UV light (FIG. 2A).

  A metal mask is brought into close contact with the outer surface of one side of the wick 130 with respect to the surface-treated wick 130, and Cu is deposited by 0.5 μm. In the metal mask, a pattern matching the groove 120 of the groove 110 formed in the housing 101 and the lid 102 is opened. On the surface of the wick 130, the Cu vapor deposition film 131 having this opening pattern is formed. After vapor deposition on one surface, Cu vapor deposition is similarly performed on the other surface facing each other. FIG. 2B shows a state in which the metal mask is removed after vapor deposition and a Cu vapor deposition film 131 is formed.

  Subsequent to Cu deposition, Cu plating is performed by an electroless plating method. Since there is a limit to the film thickness of Cu obtained by vapor deposition, the film thickness is increased by Cu plating. The plating thickness is 30 μm. FIG. 2C shows a Cu vapor deposition film 131 and a Cu plating film 132 formed thereon (the metal pattern 150 in FIG. 1C is composed of a Cu vapor deposition film 131 and a Cu plating film 132). . FIG. 4A shows an enlarged view of the portion.

  Subsequently, the insert metal 133 is disposed on the metal pattern 150. Here, SnAg paste is applied as the insert metal 133 by a screen printing method. After printing, the SnAg paste is dried at a predetermined temperature and time. The state in which the insert metal 133 is disposed is shown in FIGS. 2 (d) and 4 (b).

  The wick 130 in which the insert metal 133 is disposed on the metal pattern 150 is accommodated in the housing 101. At this time, the metal pattern 150 and the groove 120 of the groove 110 formed in the housing 101 are aligned. FIG. 3E shows a state in which the wick 130 is housed in the casing 101 (the steam pipe 30 and the liquid pipe 40 are connected to the casing 101, and the seal member 160 is also attached. To do).

  Subsequently, the lid 102 is put on. At this time, the groove 120 of the groove 110 formed inside the lid 102 coincides with the metal pattern 150. The state where the groove 120, the metal pattern 150, and the insert metal 133 are in contact is shown in FIG. 3 (f) and FIG. 4 (c).

  With the lid closed, laser welding is applied to the gap between the casing 101 and the lid 102 to make the evaporator 100 a sealed structure. Instead of laser welding, the gap between the casing 101 and the lid 102 may be welded with a solder material (FIG. 3G).

The evaporator 100 having a sealed structure is heated to approximately 250 ° C., and the metal (Cu) that forms the groove of the metal pattern 150 and the casing 101 and the lid 102 is melted by melting the insert metal 133 (liquid phase diffusion bonding). 3 (h) and 4 (d) show a state in which the insert metal 133 is diffused and integrated into the metal pattern 150 and the groove 120 by diffusion bonding.
(Example 2)
In the first embodiment, mask deposition is performed to form the metal pattern on the outer surface of the wick 130. However, in the second embodiment, the metal pattern is formed by selective etching. FIG. 5 is an enlarged view of a portion of the outer surface of the wick 130, and a method for forming a metal pattern will be described with reference to FIG.

  First, in FIG. 5A, the surface treatment of the wick 130 is performed in the same manner as in the first embodiment, and then Cr and Cu are entirely scattered as a seed layer for Cu plating in the next process (Cu sputtering is performed after Cr sputtering). Sputtering) is performed (FIG. 5B). Here, Cr has a thickness of 0.1 μm and Cu has a thickness of 0.3 μm. Note that Cr plays a role as a cement layer for improving the adhesion of Cu to the wick 130 as a base. Cr and Cu enter the pores of the porous body by the entire surface sputtering, but this is not a problem. In addition, although the Cr / Cu film 134 is formed by sputtering here, it may be formed by vapor deposition.

  Subsequently, a resist film 135 is formed. A resist is applied to the entire outer surface of the wick 130, and a resist film 135 is formed by a normal photolithography process such as baking, exposure, and development. The resist film 135 serves as a protective film for Cu deposited in the next Cu plating. FIG. 5C shows a state in which a resist film 135 is formed.

  Cu electroplating is performed with the resist film formed. A Cu plating film 136 is formed in the opening of the resist film 135 (FIG. 5D). The plating film thickness of Cu is 30 μm.

  After the formation of the Cu plating film 136, the resist film 135 is removed, and then etching of Cu and Cr generated by sputtering is performed. The plated Cu surface is also slightly dissolved by etching, but the lowermost layer Cr is not dissolved by the masking of the Cu plating film 136, and the metal pattern 151 shown in FIG. 5 (e) is formed. Will be.

The wick 130 after the metal pattern 151 is formed is incorporated into the evaporator casing 101 in the same manner as in the first embodiment.
(Example 3)
In the first and second embodiments, the groove 110 serving as a steam passage is formed on the inner wall of the casing 101 of the evaporator 100 and the outer surface of the wick 130 is flat. This is an example in which the inner wall of the housing 201 is flat and the groove 310 is formed on the outer surface of the wick 300. In addition, the housing | casing 201 of the evaporator 200, the lid | cover 202, and the wick 300 are substantially the same shapes except for the presence or absence of a groove.

  FIG. 6A shows a state in which the surface treatment is performed in the same manner as in the first embodiment on the wick 300 in which the groove 310 is formed on the outer surface. 6A and 6B are cross-sectional views taken along the line B-B 'shown in FIG.

  After performing the surface treatment, a Cu / Cr film 301 is formed on the groove 320 of the wick 300 by mask deposition of Cr and Cu. Then, electroless plating of Cu is performed to form a Cu plating film 302 on the Cu / Cr film 301. The film thicknesses of Cr, Cu by the deposited film, and Cu by plating are the same as those in Example 1. After forming the Cu plating film 302, an SnAg paste is formed thereon as an insert metal 303 by the screen printing method in the same manner as in Example 1, and the paste is dried at a predetermined temperature and time (FIG. 6B to FIG. d)).

  Thereafter, the wick 300 is housed in the casing 201 of the evaporator 200, covered with the lid 202, and the gap is welded to form a sealed structure, and diffusion bonding is performed by heating, as in the first embodiment. That is, as shown in FIG. 7A, a wick 200 in which an insert metal is placed in a groove is housed in a casing 201 having a flat inner wall, and a lid 202 having a flat inner surface is also put on the casing 201. Laser welding is applied to the gap between the lids 202 to make the evaporator 200 a sealed structure. Then, it is heated at 250 ° C. for a predetermined time and diffusion-bonded (FIGS. 7A to 7H).

  In the above embodiment, a ceramic porous body was used as the wick, but a sintered nickel metal (for example, an average porosity of 3 μm and a porosity of 50%) or Teflon (registered trademark) powder ( For example, the average porosity may be 5 μm, and the porosity may be 40%.

  In addition, SnAg is used as the insert metal, but SnAgCu, SnBi, Sn, In, or the like may be used.

10 Evaporator 11 Groove (steam discharge groove)
12 Groove mountain 13 Wick 14 Hollow portion 20 Condenser 30 Vapor tube 40 Liquid tube 100 Evaporator 101 Housing 102 Lid 103 Welding portion 110 Groove 120 Groove mountain 130 Wick 131 Cu vapor deposition film 132 Cu plating film 133 Insert metal 134 Cr / Cu Film 136 Cu plating film 140 Hollow part 150 Metal pattern 151 Metal pattern 160 Seal member 200 Evaporator 201 Housing 202 Lid 300 Wick 301 Cu / Cr film 302 Cu plating film 303 Insert metal 310 Groove 320 Groove mountain

Claims (4)

A loop heat pipe that circulates the working fluid to the evaporator and condenser through a pipe,
The evaporator is
A housing with a groove formed on the inner wall;
Forming a metal pattern in accordance with the shape of the groove of the groove of the housing on the outer wall surface, and comprising a wick for evaporating the working fluid flowing in from the pipe,
A loop type characterized in that the metal that forms the groove and the metal pattern are accommodated relative to each other and the metal pattern that diffuses the metal pattern is diffused into the metal that forms the groove. heat pipe. A loop heat pipe that circulates the working fluid to the evaporator and condenser through a pipe,
The evaporator is
A housing,
Forming a groove on the outer wall, forming a metal film on a groove mountain of the groove, and a wick for evaporating the working fluid flowing from the pipe,
A loop type heat pipe characterized by diffusion bonding which diffuses the metal film of the ridge of the wick to the metal forming the inner wall of the casing. An evaporator manufacturing method for a loop heat pipe,
A metal film forming step of forming a band-shaped metal pattern with a predetermined width and interval on the upper and lower outer wall surfaces of the flat rectangular parallelepiped wick;
An insert metal placement step of placing an insert metal on the metal pattern;
A wick in which the insert metal is disposed in a metal housing of the evaporator in which a groove in which a first groove ridge is formed in accordance with the shape of the metal pattern is formed on the bottom surface of the inner wall of the flat box type is a metal on the lower surface of the wick. A metal lid on which a groove is formed in accordance with the shape of the metal pattern, and the metal pattern on the upper surface of the wick is arranged on the one surface to match the shape of the metal groove. A wick accommodation step of placing the lid in accordance with the second groove crest,
A welding step of welding a joint surface between the casing in which the wick is accommodated and the lid;
A diffusion bonding step of heating the deposited evaporator at a predetermined temperature and diffusing the insert metal into the metal pattern of the wick and the metal of the first and second grooves;
An evaporator manufacturing method for a loop heat pipe, comprising: An evaporator manufacturing method for a loop heat pipe,
A wick groove forming step for forming a belt-like groove at a predetermined width and interval on the upper and lower outer wall surfaces of the flat rectangular parallelepiped wick;
A groove mountain metal film forming step of forming a metal film on the groove mountain of the wick groove;
An insert metal placement step of placing an insert metal on the metal film;
A wick housing step of disposing a wick in which the insert metal is disposed in a metal housing of the evaporator, and placing a metal lid on the upper surface of the wick;
A welding step of welding a joint surface between the casing in which the wick is accommodated and the lid;
A diffusion bonding step of heating the deposited evaporator at a predetermined temperature and diffusing the insert metal into the metal film of the wick and the metal of the first and second grooves;
An evaporator manufacturing method for a loop heat pipe, comprising: